Natural heart valves are thin membranes which can seem to the uninitiated to be too fragile to open and close constantly hour after hour to keep a human heart pumping for a lifetime. Despite their apparent fragility, however, human heart valves are generally tough and reliable. Surgeons who repair or replace heart valves thus face a daunting challenge: to reproduce the performance and longevity of natural heart valves using tissue or synthetic materials and surgical techniques. Not surprisingly, many if not all prior art valve replacement and repair techniques have been acknowledged as only partially meeting this challenge, inasmuch as they provide only a temporary correction (10-20 years or so, and sometimes significantly less) and do not reproduce the original valve's function or efficiency.
As if the above challenges in heart valve technology were not enough, existing techniques and prostheses are also plagued by enormous costs. Understandably, synthetic structures and xenografts must be carefully engineered to create not only generally biocompatible structures but nonimmunogenic ones as well. Even seemingly safe materials such as surgical titanium and stainless steel, and polymers such as polyether polyurethane, have demonstrated troublesome biocompatibility or immunogenicity problems, and the useful life of a prosthesis incorporating them is thus unfortunately shortened. Alternative, expensive materials have been developed but even these synthetic materials and treated xenografts are imperfect.
Finally, one heart valve in particular--the mitral valve--has traditionally been less satisfactorily replaced than the other valves of the heart. (The same might be said of the mitral and tricuspid valves both, except that as a practical matter tricuspid valve replacement is not as important as mitral valve replacement--one tricuspid valve is replaced for every 1,000 mitral valves, in large part because repair can under certain circumstances succeed with annuloplasty alone.) The traditional difficulties in replacing or repairing mitral valves are due primarily to the challenge inherent in reproducing the natural valve structure including the chordae tendineae. The chordae tendineae connect the valve leaflets to the papillary muscles of the heart. Surgical replacement of the chordae tendineae in conjunction with mitral valve repair has previously been attempted, but with limited success. The area available for suturing one of the chordae directly to a papillary muscle is very small, due to the narrow width of a chord, and attempted attachment has invariably caused either the suture and/or the chord to pull free of the papillary muscle within a short time after surgery. Mitral valve replacement without reconstruction including chordae tendineae does not restore the original structure of the heart. It is helpful to note that standard trileaflet prosthetic valves for aortic or pulmonary valve replacement are not anatomically deficient with respect to their intended loci. Those same standard valves, however, cannot replace the mitral valve without anatomic compromise. A need therefore remains for a mitral (tricuspid) heart valve which can claim the same distinction.
Accordingly, a new mitral valve, and a method for replacing or repairing the mitral valve, are needed in the cardiac surgery arts. An especial need persists for a mitral valve which is biocompatible and thoroughly nonimmunogenic, can be made and surgically implanted at substantially reduced cost (in comparison to prior art mitral valves), and which accurately reproduces and restores the original anatomy of the heart including chordae tendineae. Additionally, the mitral valve should be suitable for use in the tricuspid position, in those instances in which tricuspid valve replacement is indicated.